Early diagnosis and targeted intervention based on the pathogenesis of rapidly progressive osteoarthritis of the hip

Figure 4 Illustration of the radiological parameters of the sagittal spinopelvic alignment. Pelvic tilt is the angle between the vertical and the line from the center of the femoral heads to the midpoint of the sacral endplate. Sacral slope is the angle between the horizontal and the first sacral endplate. Pelvic incidence is calculated using the following equation: Pelvic incidence = pelvic tilt + sacral slope. Sagittal vertical axis is defined as the sagittal offset of the seventh cervical vertebra plumb line from the posterosuperior corner of the first sacral endplate. Thoracic kyphosis angle is the angle between the upper endplate of the fourth thoracic vertebra and the lower endplate of the twelfth thoracic vertebra. Lumbar lordosis angle is the angle between the upper endplate of the first lumbar vertebra and the first sacral endplate. PT: Pelvic tilt; SS: Sacral slope; PI: Pelvic incidence; SVA: Sagittal vertical axis; C7: Seventh cervical vertebra; TK: Thoracic kyphosis angle; T4: Fourth thoracic vertebra; T12: Twelfth thoracic vertebra; LL: Lordosis angle.